Calcium-ion-doped modified sodium lithium titanate material, preparation method thereof, negative electrode sheet and battery
By modifying sodium lithium titanate material with calcium ion doping, the problems of electronic conductivity and lithium ion migration dynamics of Na2Li2Ti6O14 anode material were solved, achieving high conductivity and stable electrochemical performance, and improving the cycle life and electrochemical performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU UNIV OF TECH
- Filing Date
- 2023-08-03
- Publication Date
- 2026-05-29
AI Technical Summary
The low intrinsic electronic conductivity and low lithium-ion migration kinetics of Na2Li2Ti6O14 anode material result in poor rate performance and cycle stability, limiting its practical application in high current density applications.
By modifying sodium lithium titanate materials with calcium ion doping, and combining the sol-gel method with the high-temperature solid-state method, modified sodium lithium titanate materials with expanded lattice spacing were prepared, thereby improving the lithium ion insertion/extraction rate and electronic conductivity.
It improves the structural stability and electronic conductivity of the material, enhances the cycle life and electrochemical performance of the battery, reduces the manufacturing cost, and meets the requirements for performance and cycle life.
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Figure CN116835637B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery anode material technology, and particularly to a calcium ion-doped modified sodium titanate material, its preparation method, anode sheet, and battery. Background Technology
[0002] Lithium-ion batteries have been extensively studied over the past 20 years due to their advantages such as high cycle stability, large capacity, and light weight. Anode materials are a crucial component of lithium-ion batteries, directly affecting their electrochemical performance. However, traditional carbon-based anode materials have consistently suffered from poor safety and high cycling rates, failing to meet the demands of modern society, especially in the electric vehicle field. Other potential-based anode materials, such as silicon-based and tin-based materials, have attracted widespread attention due to their high theoretical capacity. However, the practical application of these anode materials is hindered by the drastic specific volume change during Li insertion / extraction, leading to poor cycle stability. Titanium-based anode materials, especially Li₄Ti₅O₅, are also noteworthy. 12 It has attracted much attention due to its excellent structural stability and high safety. However, in Li4Ti5O 12 The high concentration of lithium found in it increased Li4Ti5O 12 The cost of lithium-ion batteries. Furthermore, a high-voltage platform reduces the overall energy density of the lithium-ion battery.
[0003] Therefore, it is essential to develop novel titanium-based anode materials with low lithium concentration, low voltage plateau, and excellent structural stability. Recently, a novel titanate anode material, Na₂Li₂Ti₆O, was discovered. 14 It has more than Li4Ti5O 12 Lower discharge plateau: Exhibits a low voltage plateau (~1.25V, vs. Li0 / Li+), which can increase the voltage of the full cell when used as the negative electrode. When Na2Li2Ti6O 14 Ti 4+ Completely restored to Ti 3+ It possesses a theoretical specific capacity of 281 mAh / g. Furthermore, since sodium is cheaper than lithium, Na₂Li₂Ti₆O₅... 14 The cost of the base anode material may be lower than that of Li4Ti5O. 12 While lithium sodium titanate is a basic anode material, its poor conductivity, reversible capacity, and cycle stability limit all its properties in high current density applications, thus restricting its practical use.
[0004] Therefore, Na2Li2Ti6O 14The practical application of anode materials remains a challenge because their limited diffusion kinetics and low intrinsic electronic conductivity result in poor rate performance and poor cycling stability at high rates, thus limiting their practical application. Summary of the Invention
[0005] In view of this, embodiments of this application provide a calcium ion-doped modified sodium titanate lithium material, its preparation method, a negative electrode, and a battery, to solve the problem of Na2Li2Ti6O 14 Addressing the technical challenges of low intrinsic electronic conductivity and low lithium-ion migration kinetics, this application utilizes Li vacancy doping in lithium sodium titanate to increase its lattice spacing, thereby enabling rapid lithium-ion insertion and extraction. The aim is to provide calcium-doped Na₂Li₂Ti₆O₄. 14 In this application, a modified lithium sodium titanate material with excellent electrochemical performance and excellent cycle stability is prepared by combining the sol-gel method with the high-temperature solid-phase method and doping calcium ions through the improved sol-gel method.
[0006] The first aspect of this application provides a calcium ion-doped modified sodium lithium titanate material, the chemical formula of which is: Na₂Ca x Li 2-x Ti6O 14 , where the range of x is 0≤x≤0.30.
[0007] In some embodiments that may include the above embodiments, the value of x is 0.05, 0.1, or 0.15.
[0008] The second aspect of this application also provides a method for preparing a calcium ion-doped modified sodium titanate lithium material, comprising the following steps:
[0009] Step 1: Weigh the calcium source, lithium source, and sodium source according to the stoichiometric ratio of the chemical formula of the modified sodium lithium titanate material, with the lithium source added in excess by 10%, and weigh a certain amount of complexing agent, dissolve it in an appropriate amount of solvent, perform ultrasonic vibration and stir evenly to obtain solution A.
[0010] Step 2: Weigh a certain amount of titanium source, dissolve it in an appropriate amount of ethanol, stir well, and obtain solution B;
[0011] Step 3: Mix solution A and solution B to obtain solution C;
[0012] Step 4: Stir the solution C until homogeneous and process it into precursor gel D;
[0013] Step 5: Grind the precursor gel D to obtain precursor powder E;
[0014] Step 6: Calcine the precursor powder E under an inert atmosphere, and ball mill the calcined product to obtain calcium ion-doped modified sodium titanate lithium material.
[0015] The excess lithium source is to compensate for the loss of lithium during high-temperature sintering. The role of ultrasonic mixing and homogenization is to crush the insoluble solids in the liquid into finer particles and mix them thoroughly with the surrounding liquid to form an emulsion. Ball milling of the sintered material can reduce the particle size of the modified sodium titanate lithium material, mechanically alloy it, and change the shape of the particles.
[0016] In some embodiments that may include the above embodiments, the specific steps include:
[0017] Step 1: Weigh the calcium source, lithium source, and sodium source according to the stoichiometric ratio of 1:1:1 according to the chemical formula of the modified sodium lithium titanate material, with the lithium source added in excess of 10%, and the calcium source weighed at 5wt%, 10wt%, and 15wt% by mass, respectively; weigh 10wt% citric acid, dissolve it in a mixture of 10ml ethanol and 10ml plasma water, and sonicate the mixture for 30-60 minutes to homogenize the particles. Then stir the mixture on a stirrer for 2 hours to obtain solution A.
[0018] Step 2: Weigh 5 mmol of titanium source, dissolve it in 10-20 mL of ethanol, and heat and stir in a constant temperature stirrer at 80 °C for 20-30 min to obtain solution B;
[0019] Step 3: Slowly add solution A dropwise to solution B and mix them while vigorously stirring solution B to obtain solution C;
[0020] Step 4: Dry the solution C in an oven at 80-100℃ for 8-12 hours until the solvent evaporates, and process it into precursor gel D;
[0021] Step 5: Grind the precursor gel D to obtain precursor powder E;
[0022] Step 6: The precursor powder E is calcined in a tube furnace under an argon atmosphere at a temperature of 600-900℃ for 8-10 hours. The sintered product is then ball-milled in a high-energy vibrating ball mill to obtain calcium ion-doped modified sodium titanate material.
[0023] In some embodiments that may include the above embodiments, the titanium source is tetrabutyl titanate or titanium dioxide.
[0024] In some embodiments that may include the above embodiments, the sodium source is one or more of sodium acetate, sodium chloride, and sodium carbonate.
[0025] In some embodiments that may include the above embodiments, the lithium source is one or more of lithium acetate, lithium carbonate, and lithium hydroxide.
[0026] In some embodiments that may include the above embodiments, the calcium source is one or more of calcium carbonate, calcium acetate, and calcium chloride.
[0027] A third aspect of this application also provides a negative electrode sheet containing the above-described modified lithium sodium titanate material or a modified lithium sodium titanate material prepared by the above-described method.
[0028] The fourth aspect of this application also provides a battery, which includes the above-described negative electrode, and further includes a battery casing, a positive electrode, a separator, and an electrolyte.
[0029] Compared with the prior art, the embodiments of this application have the following beneficial effects:
[0030] 1. In this application, the doping of calcium ions results in uniform particle size, stable and dense structure of the modified sodium lithium titanate material. Due to the larger Ca... 2+ Occupying a smaller Li + The location, and a certain amount of Ti 3+ Ions to Ti 4+ The transition of ions serves as charge compensation. Therefore, as the lattice expands to a certain extent, the expansion channels reduce the obstruction to Li ion diffusion, thereby improving the ionic conductivity of lithium sodium titanate. On the one hand, this can improve the structural stability of lithium sodium titanate, slow down structural changes and capacity decay rates, and improve the cycle life of the battery. On the other hand, the doping of calcium ions in this application can improve the electronic conductivity of lithium sodium titanate.
[0031] 2. The preparation method used in this application is simple, rapid, and uses inexpensive raw materials. First, inexpensive and readily available starting materials are selected, and a precursor gel is obtained using the sol-gel method. After grinding the gel into powder, the precursor powder is calcined in a tube furnace under an argon atmosphere to obtain the product. This synthesis method does not require expensive raw materials, equipment, or complex synthesis conditions, greatly reducing the complexity and cost of the preparation process, and has practical application value.
[0032] 3. This application has prepared a material with excellent electrochemical performance. In electrochemical tests, the material exhibits high discharge specific capacity, low internal resistance and good cycle life, which indicates that the material has potential in lithium-ion battery applications and can meet the requirements of both performance and cycle life. Attached Figure Description
[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 The XRD patterns of the calcium ion-doped modified sodium titanate lithium materials of Examples 1-3 of this application are shown below.
[0035] Figure 2 This is a magnification diagram of the pure sodium lithium titanate material of Comparative Example 1 of this application;
[0036] Figure 3 This is a long-cycle diagram of the pure sodium lithium titanate material of Comparative Example 1 of this application;
[0037] Figure 4 This is a magnification diagram of the calcium ion-doped modified sodium titanate lithium material of Example 1 of this application;
[0038] Figure 5 This is a long-cycle diagram of the calcium ion-doped modified sodium titanate lithium material of Example 1 of this application;
[0039] Figure 6 This is a SEM image of the calcium ion-doped modified sodium titanate lithium material of Example 1 of this application;
[0040] Figure 7 This is a SEM image of the pure sodium lithium titanate material of Comparative Example 1 of this application. Detailed Implementation
[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0042] Experimental methods not specifically described in the following examples are generally performed according to national standards; if no corresponding national standard exists, they are performed according to generally accepted international standards or standards known in the art. Unless otherwise stated, all parts are parts by weight and all percentages are weight percentages.
[0043] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially, as follows: lithium acetate (Shanghai Maclean Biochemical Technology Co., Ltd., 99%), sodium acetate (Shanghai Maclean Biochemical Technology Co., Ltd., 99%), citric acid (Jiangsu Qiangsheng Functional Chemical Co., Ltd., analytical grade), and tetrabutyl titanate (Wuxi Zhanwang Chemical Reagent Co., Ltd., chemically pure).
[0044] Comparative Example 1
[0045] First, weigh out 5 mmol of sodium acetate, 5 mmol of lithium acetate, and 5 mmol of citric acid and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it for 1 hour in an ultrasonic cleaner to obtain solution A. Next, weigh out 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80 °C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100 °C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, then calcine it at 700 °C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibration ball mill for 2 hours to obtain pure sample Na2Li2Ti6O. 14 Electrode materials.
[0046] Example 1
[0047] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 5 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80 °C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100 °C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, then calcine it at 700 °C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibratory ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.05 Li 1.95 Ti6O 14 Electrode materials.
[0048] Example 2
[0049] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 10 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80 °C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100 °C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, then calcine it at 700 °C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibratory ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.1 Li 1.9 Ti6O 14 Electrode materials.
[0050] Example 3
[0051] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 15 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80 °C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100 °C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, and then calcine it at 700 °C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibratory ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.15 Li 1.85 Ti6O 14 Electrode materials.
[0052] Example 4
[0053] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 5 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80°C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100°C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, then calcine it at 600°C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibration ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.05 Li 1.95 Ti6O 14 Electrode materials.
[0054] Example 5
[0055] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 5 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80 °C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100 °C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, then calcine it at 800 °C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibratory ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.05 Li 1.95 Ti6O 14 Electrode materials.
[0056] Example 6
[0057] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 5 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80°C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100°C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, and then calcine it at 900°C for 10 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibration ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.05 Li 1.95 Ti6O 14 Electrode materials.
[0058] Example 7
[0059] First, weigh 5 mmol of sodium acetate, 5 mmol of lithium acetate, 5 mmol of citric acid, and 5 wt% of calcium carbonate and dissolve them in a mixed solution of 10 mL of plasma water and 10 mL of ethanol. Stir the solution thoroughly in a beaker and sonicate it in an ultrasonic cleaner for 1 hour to obtain solution A. Next, weigh 5 mmol of tetrabutyl titanate and slowly add it dropwise to a solution of 15 mL of ethanol. Heat and stir the solution at 80 °C for 25 minutes to obtain solution B. Slowly add solution B dropwise to solution A while vigorously stirring solution A. After stirring the above solutions for 2 hours to mix thoroughly, dry them in an oven at 100 °C for 12 hours. Remove the dried gel, grind it in a mortar for 30 minutes, then calcine it at 700 °C for 8 hours under an argon atmosphere. Finally, ball mill the sintered material in a high-energy vibration ball mill for 2 hours to obtain calcium ion-doped modified Na₂Ca. 0.05 Li 1.95 Ti6O 14 Electrode materials.
[0060] Example 8 XRD Test
[0061] The materials prepared in Examples 1-3 were subjected to XRD tests, and the test results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the main diffraction peaks of the calcium ion-doped modified lithium sodium titanate materials prepared with different doping ratios are in the same position, and all the main diffraction peaks are basically consistent with the standard spectrum of lithium sodium titanate (PDF#52-0690), indicating that the synthesized product has achieved the expected goal.
[0062] Example 9: SEM Testing
[0063] The material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 6 As shown. From Figure 6 It can be seen that the powder formed aggregates composed of fine rod-shaped particles. A pure sodium titanate lithium sample from Comparative Example 1 was subjected to SEM testing, and the results are as follows... Figure 7 As shown. Comparison Figure 6 and Figure 7 It can be seen that calcium ions have been successfully doped.
[0064] Example 10 Battery Performance Test
[0065] The product of Example 1 was used as an electrode material for lithium-ion batteries.
[0066] (1) The material of Example 1 was mixed with conductive agent Super P and PVDF in a mass ratio of 8:1:1. The mixture was ground in a mortar and mixed evenly. An appropriate amount of NMP was added and coated onto copper foil. The mixture was placed in a vacuum drying oven and dried at 80°C for 12 hours. After rolling and cutting, the negative electrode sheet of the battery was obtained.
[0067] (2) Using lithium metal sheets as the counter electrode, a 2016-type button cell was fabricated in an argon-filled glove box. A Celgard 2250 separator was used, and a 1M LiPF6 / EC:DEC electrolyte (volume ratio 1:1) was used. The fabricated 2016-type button cell was then tested on a Blue Electric testing system to assess its performance. The electrochemical energy storage performance of the fabricated lithium-ion battery was also tested.
[0068] (3) The charge / discharge range is 0.01-3V, and the charge / discharge rates are 0.1A / g, 0.2A / g, 0.3A / g, 0.5A / g, and 0.1A / g. The electrochemical energy storage performance of the prepared lithium-ion battery was tested, such as... Figure 4 , Figure 5 As shown.
[0069] Depend on Figure 4 It can be seen that the Na2Ca prepared using Example 1 0.05 Li 1.95 Ti6O 14 The composite material exhibits discharge specific capacities of approximately 231.8 mAh / g, 123 mAh / g, 104.7 mAh / g, and 92.9 mAh / g at different charge / discharge current densities of 0.1 A / g, 0.2 A / g, 0.3 A / g, and 0.5 A / g, with capacity retention rates of 94.72%, 97.07%, 98.33%, and 98.84%, respectively. This indicates that the material possesses good cycle performance and high coulombic efficiency.
[0070] Depend on Figure 5 It can be seen that the Na2Ca prepared using Example 1 0.05 Li 1.95 Ti6O 14After 100 cycles at a current density of 100 mA / g, the composite material still retains a specific capacity of approximately 146.8 mAh / g, with a capacity retention of approximately 98.09%. This indicates that the material exhibits good cycling performance and high coulombic efficiency.
[0071] The product from Comparative Example 1 was used as an electrode material for lithium-ion batteries using the same method described above. The result was as follows: Figure 2 and Figure 3 The performance graph shown.
[0072] Depend on Figure 2 and Figure 4 The comparison shows that the Na2Ca prepared in Example 1... 0.05 Li 1.95 Ti6O 14 The composite material exhibits superior charge-discharge capacity and cycle stability at different rates compared to Na₂Li₂Ti₆O prepared in Comparative Example 1. 14 Pure sample material; from Figure 3 and Figure 5 The comparison shows that the Na2Ca prepared in Example 1 0.05 Li 1.95 Ti6O 14 The composite material exhibits superior specific capacity and cycling stability over long cycles compared to Na₂Li₂Ti₆O prepared in Comparative Example 1. 14 Pure sample material.
[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A method for preparing a calcium ion-doped modified sodium titanate lithium material, characterized in that, The chemical formula of the modified sodium titanate lithium material is: Na₂Ca x Li 2-x Ti6O 14 The range of x is 0. <x≤0.30; The method for modifying the sodium lithium titanate material includes the following steps: Step 1: Weigh the calcium source, lithium source, and sodium source according to the stoichiometric ratio of the chemical formula of the modified sodium lithium titanate material, with the lithium source added in excess by 10%, and weigh a certain amount of complexing agent, dissolve it in an appropriate amount of solvent, perform ultrasonic vibration and stir evenly to obtain solution A. Step 2: Weigh a certain amount of titanium source, dissolve it in an appropriate amount of ethanol, stir well, and obtain solution B; Step 3: Mix solution A and solution B to obtain solution C; Step 4: Stir the solution C until homogeneous and process it into precursor gel D; Step 5: Grind the precursor gel D to obtain precursor powder E; Step 6: Calcine the precursor powder E under an inert atmosphere, and ball mill the calcined product to obtain calcium ion-doped modified sodium titanate lithium material.
2. The method for preparing the modified sodium lithium titanate material according to claim 1, characterized in that, The value of x is 0.05, 0.1 or 0.
15.
3. The method for preparing the modified sodium lithium titanate material according to claim 1, characterized in that, Specifically, the following steps are included: Step 1: Weigh the calcium source, lithium source, and sodium source according to the stoichiometric ratio of 1:1:1 according to the chemical formula of the modified sodium lithium titanate material, with the lithium source added in excess of 10%; weigh the citric acid, dissolve it in a mixture of 10 ml ethanol and 10 ml plasma water, and sonicate the mixture for 30-60 min to homogenize the particles. Then stir the mixture on a stirrer for 2 h to obtain solution A. Step 2: Weigh 5 mmol of titanium source, dissolve it in 10-20 mL of ethanol, and heat and stir in a constant temperature stirrer at 80 °C for 20-30 min to obtain solution B; Step 3: Slowly add solution A dropwise to solution B and mix them while vigorously stirring solution B to obtain solution C; Step 4: Dry the solution C in an oven at 80-100℃ for 8-12 hours until the solvent evaporates, and process it into precursor gel D; Step 5: Grind the precursor gel D to obtain precursor powder E; Step 6: The precursor powder E is calcined in a tube furnace under an argon atmosphere at a temperature of 600-900℃ for 8-10 hours. The sintered product is then ball-milled in a high-energy vibrating ball mill to obtain calcium ion-doped modified sodium titanate lithium material.
4. The method for preparing the modified sodium lithium titanate material according to claim 1, characterized in that, The titanium source is tetrabutyl titanate or titanium dioxide.
5. The method for preparing the modified sodium lithium titanate material according to claim 1, characterized in that, The sodium source is one or more of sodium acetate, sodium chloride, and sodium carbonate.
6. The method for preparing the modified sodium lithium titanate material according to claim 1, characterized in that, The lithium source is one or more of lithium acetate, lithium carbonate, and lithium hydroxide.
7. The method for preparing the modified sodium lithium titanate material according to claim 1, characterized in that, The calcium source is one or more of calcium carbonate, calcium acetate, and calcium chloride.
8. A negative electrode sheet, characterized in that, The negative electrode contains modified sodium titanate lithium material obtained by the preparation method according to any one of claims 1 to 7.
9. A battery, characterized in that, The battery includes the negative electrode sheet as described in claim 8, and further includes a battery casing, a positive electrode sheet, a separator, and an electrolyte.